Anchorage of assemblies of wires or cables



Dec. 3, 1963 E. FOUGEA ,112,

ANCHORAGE OF ASSEMBLIES OF WIRES OR CABLES Filed Sept. 15, 1961 M 0\ 2 z \\9 LL. I g

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United States Patent 3,112,544 ANCHORAGE 0F ASSEMBLIES 0F W 0R CABLES Edouard Fougea, Neuilly-sur-Seine, France, assignor to Constructions Edmond Coignet, Paris, France, a corporation of France Filed Sept. 15, 1951, Ser. No. 138,504 Claims priority, application France Mar. 2, 1961 2 Claims. (Cl. 24-426) The present invention relates to a device intended for the anchorage of assemblies of wires or cables, especially for the tensioning of pre-stressing wires for concrete constructions.

A known device of this kind enables the wires to be gripped between two conical members, male and female; this has a number of disadvantages, amongst which it should be noted that it sometimes happens, following the breaking of a wire, that the energy thus liberated is sufficient to cause the violent expulsion of the male element from the female element. Another device has already been proposed for overcoming this drawback, in which the anchorage of the wires is obtained by wedging these wires distributed around the cylindrical rod of a mandrel, between this mandrel and the wall of the cylindrical bore of a matrix through which the wires pass, the mandrel being forcibly driven into the matrix.

The mandrel and the corresponding bore are of elongated shape, and the material of the mandrel and the matrix has mechanical properties comparable with those of the material of the wires.

Good results are obtained with this device, on condition that the value of the tractive pull applied on the wires is maintained below the value of the force necessary to introduce the mandrel and the wires in the matrix.

The present invention has for its object the construction of an anchorage device of this kind, having an improved resistance to tensile stresses for the same force of intro duction required.

In accordance with the invention, the cylindrical rod of the mandrel is extended by a head having a diameter substantially greater than that of the rod and being connected to this latter by a flat abutment face for the extremities of the wires.

In this way, during the introduction of the mandrel into the matrix, for example by axial thrust on the head of the said mandrel, the wires are in contact with the said head and move forward with the mandrel, the frictional forces to be overcome being those resulting from contact between the wires and the matrix.

The progressive movement can continue in this way until the head is in contact with the entry face of the matrix, either directly or through the intermediary of a ring previously passed over the bundle of wires, and intended to prevent buckling of these wires.

The device being thus placed in position, if a tractive pull is applied to the wires, in order that the latter may slide, it is necessary not only to overcome the frictional forces between the wires and the matrix, but also between the wires and the mandrel, since the mandrel is held fixed by its head and cannot follow the wires in their forward movement.

There is thus obtained an increased strength with respect to tractive forces.

The characteristic features and advantages of the invention will be more clearly brought out from the description which follows below of one form of the construction of the anchoring device according to the invention, given solely by way of example, reference being made to the accompanying drawing, in which:

FIGURE 1 is a diagrammatic view of an anchorage device according to the invention, shown in longitudinal cross section; and 7 FIGURE 2 is an end view of this anchorage device, taken from the left end in FIGURE 1.

In this form of embodiment, the mandrel 10 comprises a cylindrical rod 11, of which one extremity 12 is frustoconical, while the other extremity is terminated by a cylindrical head 13 having a diameter substantially greater than that of the rod. This head 13 is connected to the rod 11 by a fiat bearing surface 14 perpendicular to the axis of the mandrel. The matrix 16 is formed by a cylindrical block, in the axis of which is formed a bore 17 also cylindrical and preferably coupled to the entry face 18 of this matrix by a fillet 19. The said matrix comprises a small anchorage collar 20 including this entry face. The mandrel and the bore 17 are of elongated shape, the length of the rod 11 being for example equal to about five times its diameter.

The matrix 16 and the mandrel 10 are made of a material Which has mechanical properties comparable with those of the tensioning wires 21.

These wires 21 which are arranged along the generator lines of a cylinder, pass through the bore of the matrix and surround the rod 11 of the mandrel 10, the extremities resting on the face 14 of the head of the mandrel.

In order to prevent buckling of the wires during their wedging between the mandrel and the matrix, a cylindrical ring 22 is threaded over the said wires and is placed in the vicinity of the head. The internal diameter of this ring is determined so as to permit easy introduction of the wires and the mandrel into the ring.

This ring, which does not require mechanical properties as high as the mandrel and the matrix, may be made for example of semi-hard steel of current quality.

The diameter of the bore of the matrix is less by a pre-determined amount than the diameter of the mandrel rod, increased by twice the diameter of the wires, so that the introduction in the matrix of the mandrel surrounded by the wires determines the wedging of these latter between the mandrel and the matrix.

This introduction is effected by force, a thrust being for example applied on the head of the mandrel, while the matrix is held in position, so that the ring 22 is in abutment at the same time against the matrix by its face 18 and against the mandrel by its face 14.

The introducing force applied produces a crushing action on the wires in contact with the mandrel and the matrix, together with an expanding action on the matrix and a contraction of the mandrel, and must overcome in particular the friction forces existing between the wires and the inner surface of the bore 17.

Experience has shown that the effort of introducing the mandrel in the matrix is substantially proportional to the length of rod already engaged, the mandrel playing only the part of an elastic core during the introduction process.

The introduction force is of course a function, not only of the nature of the wires, the mandrel and the matrix, but also of the diameters of the various members.

Whereas with the devices of this kind utilizing a cylindrical mandrel, the tractive force applied to the wires should not in any case exceed a certain fraction of the in troduction force in order to avoid the wires and the mandrel moving forward inside the matrix, it is possible with the device described above, to apply to the wires a tractive force having a value substantially greater than the introduction force without any sliding taking place of the wires with respect to the matrix.

This tractive force can attain substantially twice the introduotion force.

In fact, when a tension is applied to the Wires, the

matrix being held fixed, the latter wires tend to pull the mandrel forward but this mandrel is in abutment against the matrix through the intermediary oi the ring 22, and in consequence it cannot move. In order to slide inside the matrix, the wires have to overcome not only the friction forces resulting from their contact with the matrix, but also those resulting from their contact with the mandrel, the latter becoming rigidly fixed to the matrix.

This is therefore the essential difference from the known devices referred to above, in which, in the event of sliding of the wires, the mandrel is simply drawn away, and there is only the action of the friction forces between the wires and the matrix.

With the device presently described, there is thus obtained, for an equal force of introduction, a margin of safety which is more than doubled with respect to that provided by the known devices referred to above, or in other words, in order to obtain the same resistance to tensile force, the introduction force to be applied to the mandrel is reduced by more than half with respect to that necessary in the above-mentioned known devices.

The possibilities of the device wcording to the invention can be still further improved by forming transverse striations in the surface of the mandrel, or any other relief which makes this surface rough, the friction forces created between the mandrel and the wires when a tractive eiiort is applied to these latter being thus increased, and in consequence, the resistance to the tractive force being generally increased, whereas the introduction force remains unchanged.

The invention is naturally not limited to the form of embodiment described and shown, which has only been given by way of example, but includes on the contrary all the various alternatives which may be constructed within the scope of the invention. For example, it is thus possible to give the section of the mandrel and the corresponding bore of the matrix a section other than circular, and in particular this section may be polygonal. When the risk of buckling of the wires is small, the ring 22 may be dispensed with, the head 13 of the mandrel then coming directly into contact with the matrix 16.

What I claim is:

1. An anchoring device, said device comprising a mandrel having a cylindrical rod, the diameter thereof being substantially the same throughout, a matrix having a bore with a cylindrical wall, the diameter thereof being substantially the same throughout, and a plurality of wires, said mandrel and said matnix behtg made of a material having mechanical properties comparable with those of the wires, said mandrel including a head integral with one end of said rod, said head having a diameter substantially greater than said bore, said head having at its juncture with the rod a fiat abutment face perpendicular to the longitudinal axis of the mandrel, said rod and said bore being of an elongated form and the diameter of the rod and twice the diameter of said wires being greater than the diameter of said bore, whereby the introduction in the matrix of the rod surrounded by the wires with the extremities of said wires engaging the abutment face will wedge said wires between said matrix and said rod.

2. An anchoring device in accordance with claim 1, further comprising a ring having two flat pmallel faces and adapted to be threaded over the wires in contact by one of its faces with the abutment face of the mandrel head, whereby the buckling of the said Wires is avoided during the introduction of the mandrel into the matrix at the end of the introduction process.

References Cited in the file of this patent UNITED STATES PATENTS 297,155 Osgood Apr. 22, 1884 1,001,054 Lawrence Aug. 22, 1911 2,196,724 Cope Feb. 1, 1938 2,443,335 Vogel June 15, 1948. 2,587,311 Golnick Feb. 26, 1952 2,619,714 Dornaus Dec. 2, 1952 2,686,963 Freyssinet Aug. 24, 1954 2,935,776 Clark et ai. May 10, 1960 2,988,794 Gult June 2 0, 1961 3,045,305 Anderson July 24, 1962 3,048,908 Bryan Aug. 14, 1962 FOREIGN PATENTS 56,40 1 France July 23, 1952 (1st. addition of 980,702)

731,999 Germany Feb. 19, 1943 841,384 Germany June 16, 1952 1,061,859

Germany July 23, 1959 

1. AN ANCHORING DEVICE, SAID DEVICE COMPRISING A MANDREL HAVING A CYLINDRICAL ROD, THE DIAMETER THEREOF BEING SUBSTANTIALLY THE SAME THROUGHOUT, A MATRIX HAVING A BORE WITH A CYLINDRICAL WALL, THE DIAMETER THEREOF BEING SUBSTANTIALLY THE SAME THROUGHOUT, AND A PLURALITY OF WIRES, SAID MANDREL AND SAID MATRIX BEING MADE OF A MATERIAL HAVING MECHANICAL PROPERTIES COMPARABLE WITH THOSE OF THE WIRES, SAID MANDREL INCLUDING A HEAD INTEGRAL WITH ONE END OF SAID ROD, SAID HEAD HAVING A DIAMETER SUBSTANTIALLY GREATER THAN SAID BORE, SAID HEAD HAVING AT ITS 